14341 .. 6 A. EXPERIMENTAL ANIMAL DECOMPRESSIONS TO A NEAR-VACUUM ENVIRONMENT - NTRS
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
https://ntrs.nasa.gov/search.jsp?R=19660005052 2019-10-20T20:45:51+00:00Z
I
~
~ 6 14341
6 ..
I
A. EXPERIMENTAL ANIMAL DECOMPRESSIONS TO A NEAR-VACUUM ENVIRONMENT
RICHARD W. BANCROFT, Ph.D.
JAMES E. DUNN 11, Captain, W A F , MCFOREWORD
These reports were prepared in the Physiology Branch under task No. 775801. The
study was supported by contract No. DPR T-16758-G with the National Aeronautics
and Space Administration, Manned Spacecraft Center, Houston, Tex. The papers
were presented a t the Aerospace Medical Association Meeting, Miami Beach, Fla.,
on 12 May 1964 and submitted for publication on 9 April 1965.
Experiments reported herein were condurt,ed according to the “lirincipies of
Laboratory Animal Care” of the National Society for Medical Research.
The valuable technical assistance of Major William D. Habluetzel is most gratefully
acknowledged.
This report has been reviewed and is approved.
HAROLD V. ELLINGSON
Colonel, USAF, MC
CommanderABSTRACT
I '
To estimate the times of consciousness, collapse, and survival of animals exposed
to near-vacuum environments, 126 conscious dogs were rapidly decompressed in either
1 or 0.2 second.from 35,000 feet, while breathing oxygen, t o a pressure less than 2 mm.
H g absolute. Groups of 6 dogs each were exposed t o this low pressure' for periods of
time ranging from 5 t o 180 seconds, with and without prior denitrogenation, and
then recompressed t o 35,000 feet with oxygen in either 5 or 30 seconds. The dogs
collapsed within 9 t o 10 seconds after decompression, as determined from motion
picture films. Simultaneously, the effects of anoxia, water vapor, and other evolved
gases were apparent, resulting in a generalized muscle spasticity, a few gasps,
momentary convulsive seizures, apnea, and gross swelling of the body and extremities.
All dogs exposed f o r less than 120 seconds survived, despite evidence of lung involve-
ment. Respiration recommenced spontaneously either during recompression o r a t
ground level, provided the heart was beating; otherwise, death was inevitable. The
longer the exposure time, the more prolonged was the time f o r recovery which
usually ranged from a few minutes to a few hours, except f o r 1 dog which exhibited
a severe postdecompression paralysis with gradual recovery over a period of several
weeks. Exposures of 120 t o 180 seconds resulted in approximately 15% to more than
80% fatalities, respectively. Denitrogenated dogs tended to show a slightly better
survival rate. As might be expected, the shorter the exposure time and the faster
the recompression r a t e better were the chances for uneventful and
prompt recovery.
iiiEXPERIMENTAL ANIMAL DECOMPRESSIONS TO A NEAR-VACUUM ENVIRONMENT
I. INTRODUCTION The critical situation confronting an aero-
space crew should accidental loss of pressure
Despite the fact t h a t a considerable number be experienced dictated the use of physiological-
of studies have been carried out on the effects ly normal animals so that the data collected
of rapid decompression to high altitudes, there would be as valid as was possible to obtain.
is still very little information and data con- Normal, unanesthetized dogs were therefore
cerning the actual effects of exposures t o ex- used ; 126 animals were rapidly decompressed
tremely low barometric pressures-that is, to to absolute pressures of 1 to 2 mm. Hg.
pressure environments approaching the near-
vacuum of space. This information is becoming 11. METHODS
increasingly urgent in view of the current
manned space flights, the programed flights to The experimental procedures and decom-
the surface of the moon, and the need for man pression-recompression profiles are summarized
to function safely within a pressure suit in in table I.
space.
In most tests, 3 dogs were simultaneously
decompressed. The rapid decompressions were
The extensive series of studies carried out all from 35,000 feet (180 mm. Hg) with the
by Hitchcock and his co-workers ( 5 ) , as well chamber flooded with oxygen. In this way, the
as by other investigators (2, 3, 4, 6), have animals remained unrestrained and hypoxia was
defined quite clearly most of the effects of avoided at this altitude before the decompres-
rapid decompressions to at least 30 mm. H g sions. No animal was decompressed more than
absolute, using experimental animals. Whether once.
or not rapid exposures to even lower ambient
pressures approaching that of a vacuum result
in even more profound consequences cannot be TABLE I
entirely deduced from this earlier work. Some Experimental procedure
questions t h a t are still not clear, but must be
answered with a reasonable degree of confi- All decompressions from 35,000 feet
dence, are concerned with : (in oxygen)
Decompression times: 1 second (108)
1. Time of consciousness. 0.2 second (18)
Duration of exposures (6 animals in each
2. Survival time after loss of consciousness. group) 3-5, 10, 30, 60, 90, 120, 135,
150, 165,180 seconds
3. Extent and type of pathologic effects that might Recompression times: 5 seconds (84)
occur in the vital organs. 30 seconds (27)
Denitrogenation: 1 hour at ground level (42)
4. The biologic effects of interstitial and intravas-
cular water vapor. Type of recompression gas: Oxygen (117)
Room air (9)
5. The effect of .denitrogenation on the time of
consciousness, survival, recovery, and residual effects. Numbers in parentheses are number of animals.
1Decompression times from 180 to less than With these film records, the precise times for
2 mm. Hg were all approximately 1 second, complete unconsciousness and collapse could be
except for 6 faster decompressions (18 dogs) determined, as well as the time required for
which were arranged t o occur within approxi- the extensive swelling due to water vapor and
mately 0.2 second. other evolved gases. Exposure times, recom-
pression times, and the barometric pressure
Exposure times at the absolute pressure of a t which the emphysematous swelling tended t o
1to 2 mm. Hg for the various groups of animals deflate and return to normal during recompres-
ranged between 4 and 180 seconds. At least sion were also determined from these film
2 groups of 3 each were exposed to this low records.
pressure for approximately 4, 10, 30, 60, 90,
120, 135, 150, 165, and 180 seconds. In this TO establish, as well as possible, UIICOZI=
way the critical times for the onset of uncoc- piicated baselines for survivability and re-
sciousness, survival, recovery, and nonsurviva- covery, no artificial respiration or other
bility were estimated from the effects on the methods of resuscitation were used on any of
6 animals for each exposure time and for each the animals after recompression to ground level
variation in the experimental conditions-Le., pressures. Provided the pulmonary airways
rate of recompression and time for denitrogena- are open, the process of recompression itself is
tion before decompression. as effective as a deep inspiration for ventilating
the lungs, regardless of whether or not the
Recompression times to 35,000 feet (180 animals are breathing. Undoubtedly, any re-
mm. Hg) with pure oxygen were 5 seconds suscitation efforts, including the continuous
(28 decompressions, 84 dogs) and 30 seconds administration of oxygen and possibly “over-
(9 decompressions, 27 dogs), followed within compression” in a high pressure chamber, would
10 to 15 seconds by recompression to ground have been of additional benefit during the
level with room air. For comparison, 3 addi- process of recovery.
tional decompressions ( 9 dogs) were carried
out using air instead of oxygen during 5-second
recompressions. 111. RESULTS AND DISCUSSION
To determine whether or not denitrogena- Survivability, tolerance, and recovery from
tion before decompression provided any degree these severe exposures to extremely low pres-
of protection, 42 dogs (14 decompressions) sures were better than had at first been an-
breathed a high concentration of oxygen ticipated, particularly in view of the rapid onset
( > 90%) for 1 hour a t ground level in the of virtually complete anoxia, together with the
decompression chamber before the rapid ex- boiling effect and gas evolvement in the body
posures to low pressure. Decompression times, fluids and tissues.
exposure times, and recompression times for
these denitrogenated animals were similar to Most of the observations that were made at
those already described. this extremely low pressure coincided in many
respects with those previously reported by Edel-
The time course and chamber pressure mann and Hitchcock (2) for dogs exposed to
changes for each decompression were recorded 30 mm. Hg absolute. The hemorrhagic lesions
through a Statham pressure transducer on a found in these earlier investigations can, in
Honeywell Visicorder. From these records, the part, be attributed to the extremely rapid de-
time for each decompression could be accurate- compression rate, reported as 0.03 second, from
ly determined, as well as the exposure times virtually ground level pressures (750 mm. Hg)
and the recompression times. In addition, mo- (2) and from 522 mm. Hg to 87 mm. Hg in
tion pictures were obtained for a large number 0.012 second (3). The decompression phase
of the decompressions, with an appropriate in the present study was much less severe in
timer and pressure gage visible in the pictures. terms of rate and pressure change (a pressure
2change of approximately 180 mm. H g in 1 sec- postural collapse. Thus, consciousness very
ond), even though the final pressure reached probably began to fade at the 8th or 9th second,
was much lower (approximately 1 mm. Hg if not sooner, a t least for those animals ex-
absolute). posed to the low pressure for longer than
5 seconds.
Time of consciousness and collapse
With regard to human exposures to a
All animals exposed t o the low pressure vacuum under similar conditions, it is sug-
for longer than 5 seconds tended to lose con- gested from these results that, for minimal
sciousness and began t o swell and collapse loss of consciousness, recompression with
within 9 to 11 seconds. For brief exposures oxygen to at least 180 mm. Hg (35,000 feet)
of only 4 to 5 seconds with recompression to m u s t begin within 5 seconds and must be
180 mm. Hg on pure oxygeil +finite indica- completed within the next 5 seconds (although
tions of collapse were exhibited by most of the these times cannot be stated with certainty).
animals a t about the 11th or 12th second after Figure 1 shows a comparative extrapolation for
the start of the decompression, even though times of consciousness a t altitudes above
recompression was in progress or had been 55,000 feet, with less than 9 to 10 seconds
completed. Under these conditions, however, being cautiously estimated for exposure to a
with 5-second recompressions, postural unstead- vacuum on the basis of the collapse times
iness was transitory when it occurred, and ap- measured in dogs. The time of “useful” con-
parent recovery with signs of conscious sciousness appears to be less than the 12 t o
orientation was rapid. When the recompression 15 seconds t h a t have been measured in human
time to 180 mm. Hg with oxygen was prolonged subjects breathing oxygen at 50,000 t o 55,000
to 30 seconds, after 5-second exposures, a more feet (7).
profound state of collapse occurred a t about the
10th second, with recovery commencing during Water vapor effect and subcutaneous swelling
the recompression a t about 140 mm. H g after decompression
(40,000 feet). These time relationships a r e
shown in table 11. During the decompressions all animals
showed essentially the same response. Im-
The exact moment when loss of “useful” mediately after decompression, the animals
consciousness commenced was difficult t o de- exhibited excitation and increased activity for
termine merely by observation, but it must the first 5 seconds. Within t h e next 5 seconds,
certainly have begun t o occur before actual unless the animals were promptly recompressed,
they began t o show marked evidence of gas
TABLE I1 expansion and water vapor evolvement. This
was manifested by a high degree of sub-
Onset o f postural collapse a f t e r rapid cutaneous emphysema and expulsion of gas
decompression f r o m 35,000 f e e t to from the stomach and lower bowel, often with
approximately 1 mm. Hg absolute simultaneous projectile vomiting, defecation,
and urination similar to t h a t previously re-
Exposure time Recompression
L
Collapse occurred
ported by others (2, 6 ) . The water vapor
at 1 mm. H g time within effect and gas expansion were of such magni-
tude t h a t the animals became completely im-
mobilized with the extremities, neck, and body
in an extended position, similar in appearance
< 5 5 11 - 12
to an inflated goat-skin bag. Oddly enough,
< 5 30 10 the external ears and the eyeballs did not seem
> 5 6 9 - 11 to show the effects of this phenomenon and
remained essentially normal in appearance, al-
> 5 30 9-11
though the soft tissue around the eyes and face
3SECONDS
10 20 30 40 50 60 70 80
' ' ' ' " ' ' ' ' ' ' ' 0
I'
I
I
I
I
I 50
I
D
I
E
E
loo E
3
cn
cn
W
[L
a
0
[L
F
150 g
0
U
a
m
200
10 20 30 40 50 60 70 80
TIME OF CONSCIOUSNESS - SECONDS
FIGURE 1
Time of consciousness f o r hiiman rapid decompressions to 55,000 f e e t ( 7 )
with a tentative extrapolation (dashed line) t o lower pressures based on
canine data obtaiiicd at less that1 2 mm. H g absolute.
was often grossly distended, as was the tongue. recompressed. While at the low pressure, the
By the end of the first 10 seconds, as indicated saliva-like secretions and the urine became
above, all the animals appeared to be uncon- frozen and partially dehydrated. It was also
scious. This was followed by what seemed to noticed in several animals, after recompression
be a grcoicl mal convulsion, ending in apnea and to ground level, t h a t the tongue was coated
a spastic rigidity which progressed to a flaccid with ice. This was particularly true for ani-
paralysis, although the animals remained mals exposed t o the low pressure for longer
grossly distended. All the animals had entered than 2 minutes when evaporative cooling from
into this state of flaccid paralysis within about these exposed wet surfaces became increasingly
30 seconds and remained so until they were effective.
4Recompression and recovery survive. During the course of recovery, both
the heart rate and respiratory frequency in-
'
During recompression to higher pressures, creased steadily for the first 2 t o 5 minutes.
the subcutaneous gases were, of course, also Some of the animals exhibited a state of de-
recompressed and the animals quickly and cerebrate spasticity when stimulated by being
dramatically deflated to their normal ap- touched or handled. Most of the animals
pearance, still remaining, however, in an ob- started purposeful movements of the extremi-
vious state of flaccid paralysis, unconsciousness, ties and head within 10 to 15 minutes and next
and apnea. This deflation process appeared t o progressed t o a stage showing disorientation,
begin rather gradually with the onset of re- with staggering and apparent blindness. Dur-
compression. At 25 to 30 mm. Hg absolute, de- ing this time, coordinated control and strength
flation became more rapid ; at approximately in the hind legs seemed to return much more
70 mm. Hg the animals appeared to have re- slowly than in the forelimbs. By the end of
turned to their normal size. At 45 to 50 mm. 30 minutes, none of the animals exhibited ob-
Hg, however, a major portion of the deflation jective neurologic abnormalities ; nevertheless,
is complete, suggesting that water vapor is they appeared to be in a state of extreme
probably the predominant gas concerned with fatigue and exhaustion and were very lethargic.
the excessive distention of the animals. The The apparent blindness seemed to abate by
exact pressures at which the deflation process the end of the 30th minute of recovery. Those
and the condensation of water vapor occurred that were exposed to the low pressure for
was influenced, in part at least, by the sub- longer than 60 seconds excreted, after recom-
cutaneous and deep body temperatures which, pression to ground level, an excessively large
in turn, were probably affected by the duration amount of clear, saliva-like fluid from the
of the low pressure exposures and the evap- mouth; moist, basal rales were audible, sug-
orative cooling of the body surfaces. gesting pulmonary edema. By the end of 24
hours, the animals spontaneously cleared them-
The rapidity of recovery during or after selves of the rales and edema and appeared t o
recompression was generally dependent on the have normal respiratory function and behavior.
duration of the low pressure exposure, the rate
of recompression, and on whether or not the Mortality incidence
animals were recompressed with oxygen or air.
As might well be expected, the shorter the As mentioned above, all dogs exposed to the
exposure time and the faster the recompression near-vacuum environment for less than 120
with oxygen, the more rapid and less com- seconds survived with essentially uneventful
plicated was the recovery period. Animals that recoveries despite evidence of severe but tran-
were exposed to the low pressure for 90 seconds sitory lung involvement. On the other hand,
or less often began to breathe spontaneously exposure times ranging from 120 to 180 seconds
during the recompression to ground level. resulted in mortality rates of about 15% t o
When the exposures to the reduced pressure more than 8076, respectively, as shown in
were longer than 90 seconds, the depressed state figure 2. Each symbol in this figure represents
of the animals was intensified and apnea per- a group of 6 animals from which the percent
sisted for a prolonged period of time after mortality was computed. It can be noted t h a t
recompression. Under these conditions, when no deaths resulted from the 90-second ex-
first examined at ground level, the animals posures, regardless of whether the animals were
were usually apneic with variations in heart recompressed (with oxygen) to 35,000 feet
rate ranging from bradycardia to tachycardia. (180 mm. Hg) within 5 seconds or 30 seconds.
They remained apneic for varying periods of The 120-second exposures, however, resulted in
time, but spontaneous respiration always began 1 death (16.7%) in the 6 animals that were
in less than 2 to 3 minutes, provided there was recompressed in 5 seconds and 3 deaths (50%)
a heartbeat. Otherwise, when no heartbeat in the group of 6 animals that were recom-
was detectable, the animals invariably failed t o pressed in 30 seconds.
5' O 0I 8
LEGEND
' 1 SEC. DECOMPRESSION
- 5 SEC RECOMPRESSION
I SEC. DECOMPRESSION
A - 30 S F C . RECOMPRESSlON
I
0 1 SEC. DECOMPRESSION
5 SEC. RECOMPRESSION
WITH ROOM AIR
DEN ITROGENAT ION
90 105 120 135 150 165 180
'- 1 SEC. DECOMPRESSION
5 SEC. RECOMPRESSION
EXPOSURE TIME - SEC
FIGURE 2
Percent morta..ty resu ing from rapid decompression exposures to less than 2 m m . H g absolute w i t h and
without prior denitrogenation and w i t h 5- and ?)O-second recompressions to 180 mm. Hg absolute w i t h and
without oxygen as noted. Each symbol represents a group of 6 dogs. The curve f o r 5-second recompressions
( w i t h oxygen) was approximated by eye.
Of the 9 dogs that were rapidly recom- are filled with oxygen, provided the airways
pressed with room air rather than oxygen, are open. On the other hand, when room air
3 were exposed to the low pressure for 150 sec- is used, it is necessary to recompress virtually
onds and all survived. The other 6 animals to ground level pressures (750 mm. Hg) for
were exposed for 165 seconds and only 1 sur- adequate oxygenation of the lungs and blood,
vived (83.3';'( mortality.) These results, with equivalent to 180 mm. Hg (35,000 feet) when
only a limited number of animals, indicate t h a t oxygen is used.
the mortality incidence is not particularly dif-
ferent from that of animals exposed for the Dogs t h a t were denitrogenated for 1 hour
same period of time and then recompressed at ground level before decompression and then
with oxygen. There are sound reasons to be- recompressed 'with oxygen (fig. 2) had a
lieve, however, that recompression with oxygen significantly lower mortality rate ( P < .05)
provides for more rapid oxygenation of the as a result of these prolonged severe exposures.
blood at a lower pressure than when room With denitrogenation, 5 out of 6 dogs survived
a i r is used 18). As mentioned above, recom- a 165-second exposure, and 2 out of 6 survived
pression from near-vacuum conditions, regard- an exposure of 180 seconds. It may be
less of whether or not the animals are postulated t h a t t h e cerebral and other vital
breathing, is as effective as a deep voluntary tissues and fluids, when completely denitro-
inspiration. If oxygen is used as the recom- genated and fully saturated with oxygen before
pressing gas, it virtually assures t h a t the lungs decompression, permit an extra margin of
6several seconds after decompression before t h e 35,000 feet. This monkey exhibited no heart-
intracellular oxygen partial pressure decreases beat and no spontaneous respiration after
‘to profound anoxic levels. This is possibly re- reaching ground level. Except for pulmonary
flected in the longer survival time compared t o atelectasis and a few subpleural petechial
the survival time of animals t h a t were not as hemorrhages, no gross pathologic abnormalities
completely denitrogenated. were observed a t autopsy, which was performed
under water.
In general, under these conditions, t h e
shorter the exposure time and the faster t h e Residual postdecompression paralysis and
recompression rate with oxygen, t h e better a r e other nervous disorders
the chances for survival and uncomplicated re-
In only 1 animal was there clear-cut
covery (excluding the possibility of middle ear
evidence of residual central nervous system
blockage during recompression).
involvement t h a t continued to persist for 24 or
more hours after recovery from prolonged ex-
Observations made on small primates posure to the low pressure. The fact t h a t
approximately one-third of the surviving
In connection with another study carried animals were sacrificed and autopsied within
out by Rumbaugh and Ternes (lo), 20 trained 30 minutes postdecompression leaves open t o
squirrel monkeys (4 groups of 5 each) were question whether or not this small percentage
also decompressed in the same manner as (approximately 1 % ) might not be actually
described above, except t h a t no exposures to larger had all survivors been observed for at
the low pressure were longer than 90 seconds. least several days before sacrifice. It seems
reasonable t h a t t h e probability of residual
After decompression t o approximately pathologic conditions in the central nervous
1 mm. H g absolute, the squirrel monkeys ap- system would be increased considerably with
peared t o lose consciousness sooner than the increased exposure times, particularly for pro-
dogs. As with dogs, they had both tonic and longed exposures of 2 minutes or longer when
clonic seizures shortly after unconsciousness the chance for survival itself becomes marginal.
and this progressed to flaccid paralysis. Sub-
cutaneous emphysema and swelling occurred, The one dog t h a t exhibited severe postde-
but was not as marked. During and following compression paralysis had been exposed to t h e
recompression to ground level, the monkeys re- low pressure environment for 120 seconds and
covered similarly but seemed t o exhibit stag- then recompressed with oxygen t o 180 mm. H g
gering and disorientation for a longer period. in 30 seconds. After reaching ground level, t h e
dog reacted in much t h e same manner as t h e
Two monkeys died as a result of these low other animals in t h e group, with a bradycardia
pressure exposures, while no dogs died from and apnea which were quickly resolved. This
exposures t h a t were less than 120 seconds. The animal, however, manifested prolonged visual
first death occurred after a 10- to 12-second impairment, and 1 hour after the exposure had
exposure with a 30-second recompression t o not completely regained vision, as tested by
35,000 feet (180 mm. Hg) with oxygen. This reaction t o motions of objects. There were no
animal, contrary to t h a t seen in nonsurviving other overly abnormal neurologic manifesta-
dogs, had a perceptible but irregular heartbeat tions at this time compared t o the other animals
after reaching ground level, but never recovered similarly exposed. When seen approximately
spontaneous respiration. Necropsy revealed 20 hours later, this animal was unable to stand,
apparent basalar atelectasis of t h e lungs with but appeared t o be spirited and mentally alert.
a questionable perforated visceral pleura just Neurologic examination showed that the ex-
over an area of petechial hemorrhage. tremities on t h e right side were weak, with
depressed deep tendon reflexes ; while extremi-
The second fatality resulted from a 90-sec- ties on t h e left side were spastic, with hyperac-
ond exposure with a 5-second recompression to tive reflexes. The cranial nerve and pain
7response reflexes were present, and the animal that do survive show, for the most part, rela-
seemed to have unimpaired sensation to pin- tively uneventful recoveries. Only in a few
prick. There was also spastic urinary incon- rare cases where the threshold of death has
tinence. Vision appeared to be normal. During been very closely approached is it possible t o
the following days, progressive improvement demonstrate survival with clear-cut residual
occurred so that by the end of 1 week, the and, possibly, irreversible lesions of the central
animal could walk unassisted, although the ex- nervous system. Human hypoxic incidents in
tremities on the left side still showed con- aircraft (9) and low pressure experiments with
siderable impairment. At this time, a urinary animals, by Biichner (1) and others cited by
tract infection developed without fever, but was him, suggest similar conclusions.
easily controlled with antibiotics. During the
next 12 weeks, the neurologic condition im- From these observations on dogs and sms!!
proved steadily; at the end of this time, the primates, conciusions concerning survivability
animal was able te wa!k a i d run well. The and recovery indicate that the prevention of
hemiparesis was scarcely discernible by neuro- death by rescue and repressurization with
logic examination, and the spasticity of the left oxygen within the order of 90 seconds appears
side and bladder was absent.
to be feasible. The fact that a fatality from
Inasmuch as this animal had been subjected a 10-second exposure has been observed in a
to a 120-second exposure with a 30-second small primate proves that any exposure t o such
recompression, the chances of survival were low pressures involves great risk, and there
marginal. For a group of 6 or more animals can be considerable individual variations. Some
under these same conditions, about 50',: fatali- dogs have survived exposures for as long as
ties could be expected (fig. 2 ) . Thus, in many 3 minutes with apparently good recovery,
instances, animals which otherwise might show whereas one dog suffered severe but nonfatal
evidence of considerable damage t o the central damage to the central nervous system after an
nervous system probably do not survive. Those exposure of 2 minutes.
KEFERENCES
1. Buchner, F. Pathology of general oxygen de- 6. Kovalenke, Ye. A. The problem of the mechanism
ficiency. I n German aviation medicine World of development of high-altitude tissue emphy-
W a r 11, vol. I, ch. IV-0, p. 419. Washington, sema. In Sisakyan (ed.). Problems of space
D.C.: U.S. Government Printing Office, 1950. biology, vol. 2, p. 407. USSR, 1962.
2. Edelmann, A., and F. A. Hitchcock. Observations 7. Luft, U. C., H. G. Clamann, and E. Opitz. The
on dogs exposed to an ambient pressure of latency of hypoxia on exposure to altitude above
30 mm. H r . J. Appl. Physiol. 4:807 (1952). 50,000 feet. J. Aviation Med. 22:117 (1951).
3. Edelmann, A., W. V. Whitehorn, A. Lein, and
8. Luft, U. C., H. G . Clamann, and H. F. Adler.
F. A. Hitchcock. Pathological lesions produced
Alveolar gases in rapid decompression to high
by explosive decompression. J. Aviation Med.
altitude. J. Appl. Physiol. 2:37 (1949).
17:596 (194G).
4. Gelfan, S., and A. Y. Werner. Cardiovascular re- 9. Luft, U. C. Altitude sickness. In Armstrong,
sponses f o l h i n g explosive decompression of H. G . (ed.). Aerospace medicine, ch. 9, p. 139.
macaque monkeys to extreme altitudes. J. Appl. Baltimore: Williams and Wilkins, 1961.
Physiol. 4:280 (1951).
10. Runibaugh, D. M., and J. W. Ternes. Learning
5. Hitchcock, F. A. Studies in explosive decompres- set performance of squirrel monkeys a f t e r rapid
sion. WADC-TK 53-191, Wright-Patterson decompression to vacuum. Aerospace Med. 36:8
AFB, Ohio, 1953. (1965).
8You can also read
